Formation of polycrystalline BaSi2 films by radio-frequency magnetron sputtering for thin-film solar cell applications

The BaSi 2 semiconductor is a promising candidate for an earth-abundant solar cell absorber. In this study, we have realized a crack-free BaSi 2 film by a simple thermal evaporation technique on a CaF 2 substrate at a growth temperature of 500 • C for electrical characterization. A Si layer preliminarily formed on the substrate by sputtering is a key to obtain stoichiometric BaSi 2 film. Detailed structural characterization of the evaporated films with different Si layer thicknesses by X-ray diffraction, scanning and transmission electron microscopy demonstrates that a crack-free 370-nm-thick BaSi 2 film is formed by consuming the Si layer. It is observed that the 90-nm-thick bottom part is microcrystalline and contains Ar atoms, which come from Si deposition atmosphere. The surface of the BaSi 2 layer is found to be covered by an amorphous Si layer due to Si-rich vapor at the last stage of evaporation. Electrical properties of the BaSi 2 film is revealed by Hall measurement and the electron density and mobility are found to be 6×10 20 cm −3 and 0.04 cm 2 /V·s, respectively. Owing to a better crystalline quality contributed by the preliminarily-deposited Si layer, minority-carrier lifetime of the evaporated film (0.6 µs) is twenty times longer than previous films on glass substrates.

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“…BaSi 2 films can be grown by the molecular beam epitaxy (MBE) [6,7], radio-frequency sputtering [8,9], and vacuum evaporation techniques [10,11].…”

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confidence: 99%

Structural and electrical characterizations of crack-free BaSi2 thin films fabricated by thermal evaporation

et al. 2015

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“…On the other hand, for BaSi 2 , a film thickness of <1 µm is commonly used in various experimental studies. [3][4][5][6][7][8][9]22,26) However, it yields a band-gap energy of 1.3 eV. 22,26) In addition, sample quality, growth conditions, and impurities also affect the photoabsorption properties.…”

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BaSi₂as a promising low-cost, earth-abundant material with large optical activity for thin-film solar cells: A hybrid density functional study

Kumar

Umezawa

Imai

2014

Appl. Phys. Express

109

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Employing a hybrid density functional theory, we reveal the origin of the large absorption coefficient in BaSi 2 , which is roughly two to eighty times larger at ħω % E g = 0.5 eV than other conventional absorbers such as Si, GaAs, CdTe, CuInSe 2 , and Cu 2 ZnSnS 4 . This is explained on the basis of the electronic band structure of BaSi 2 , whereby the lowest conduction band (CB) has a small dispersion, owing to the localized Ba-d states, resulting in flat bands. Consequently, these flat bands contribute to a wide range of optical absorption in the low-energy region and lead to high optical activity in BaSi 2 .

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“…However, the grown films contain metallic phases such as Ba 2 Si and Ba 5 Si 3 . We have succeeded in fabricating polycrystalline BaSi 2 films on Si(111) substrates by radio-frequency (RF) magnetron sputtering using crystalline BaSi 2 target at RT, followed by post-annealing at 600-700 ºC in UHV [10]. In this study, improving from the previous method, we have deposited polycrystalline BaSi 2 films on glass substrate by sputtering crystalline BaSi 2 target at 600 ºC.…”

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Fabrication and characterization of polycrystalline BaSi₂ by RF sputtering

Latiff

Yoneyama

Shibutami

et al. 2013

Phys. Status Solidi C

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Formation of polycrystalline BaSi2 films by radio-frequency magnetron sputtering for thin-film solar cell applications

Cited by 33 publications

References 32 publications

Structural and electrical characterizations of crack-free BaSi2 thin films fabricated by thermal evaporation

Structural and electrical characterizations of crack-free BaSi2 thin films fabricated by thermal evaporation

BaSi₂as a promising low-cost, earth-abundant material with large optical activity for thin-film solar cells: A hybrid density functional study

Fabrication and characterization of polycrystalline BaSi₂ by RF sputtering

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Formation of polycrystalline BaSi2 films by radio-frequency magnetron sputtering for thin-film solar cell applications

Cited by 33 publications

References 32 publications

Structural and electrical characterizations of crack-free BaSi2 thin films fabricated by thermal evaporation

Structural and electrical characterizations of crack-free BaSi2 thin films fabricated by thermal evaporation

BaSi2as a promising low-cost, earth-abundant material with large optical activity for thin-film solar cells: A hybrid density functional study

Fabrication and characterization of polycrystalline BaSi2 by RF sputtering

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Product

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BaSi₂as a promising low-cost, earth-abundant material with large optical activity for thin-film solar cells: A hybrid density functional study

Fabrication and characterization of polycrystalline BaSi₂ by RF sputtering